1. Field
An aspect of the present invention relates to an organic light emitting device with enhanced life span, and a manufacturing method of the same.
2. Description of the Related Art
In a display field, an organic light emitting device has recently been spotlighted. Such an organic light emitting device uses light generated by luminescence decay through a combination of electrons and holes.
The organic light emitting device basically includes an electrode for hole injection, an electrode for electron injection, and a light emitting layer, and has a structure that a light emitting layer is interposed between the electrode (anode) for hole injection and the electrode (cathode) for electron injection. Specifically, in the organic light emitting device, electrons are injected at a cathode, and holes are injected at an anode. Then, the electrons and the holes are moved in opposite directions by an outer electric field, are combined in the light emitting layer, and emit light through luminescence decay. In such an organic light emitting device, the light emitting layer is made of a monomolecular organic material or a polymer.
FIG. 1 is a schematic view illustrating the concept of an organic light emitting device.
Referring to FIG. 1, the organic light emitting device basically has a structure where on a substrate 10, a first electrode 20 is formed, on the first electrode 20, an organic layer 30 is disposed, and on the organic layer 30, a second electrode 40 is disposed. Herein, between the first electrode 20 and the second electrode 40, the organic layer 30 is disposed, and the organic layer 30 includes a light emitting layer in which luminescence decay occurs through a combination of holes and electrons. One of the first electrode and the second electrode is an anode for hole injection, and the other is a cathode for electron injection.
FIG. 2 shows an example of a multi-layered structure of the organic layer 30 in the organic light emitting device. In the organic layer 30, an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer are sequentially layered. If the first electrode 20 is an anode, and the second electrode is a cathode, a hole injection layer 31, a hole transport layer 32, a light emitting layer 33, an electron transport layer 34 and an electron injection layer 35 are sequentially layered. On the other hand, if the first electrode 20 is a cathode and the second electrode is an anode, an electron injection layer 31, an electron transport layer 32, a light emitting layer 33, a hole transport layer 34, and a hole injection layer 35 are sequentially layered. Also, in many cases, the electron injection layer is made of a metal element or a compound thereof instead of an organic material, and thus may be considered as a separate layer without being included in the organic layer.
Such an organic light emitting device includes a plurality of pixels such as red, green, and blue pixels. With various combinations of these pixels, a full range of colors can be emitted. The pixels of the organic light emitting device are made of light emitting materials, and the light emitting materials have different life spans according to their kinds. A pixel made of a material having a short light emitting life span cannot emit a color having its own original color coordinate as time goes on. This makes it difficult to emit characteristic color of its own such as red, green and blue. Furthermore, when the colors are combined to obtain other required colors, it may be impossible to emit a required color due to a pixel having a short light emitting life span.
In order to prolong the life span of a light emitting material and an organic light emitting device using the material, various structures and materials have been researched. However, there is a problem in that the improvement of the life span of the light emitting material deteriorates other properties.
Accordingly, it is required to develop a light emitting material and a device structure, which can maintain luminous efficiency and operating characteristics while improving the life span.